Optical Disk Apparatus with an Improved Track Jump Performance

ABSTRACT

An optical disk device for recording or reproducing an optical disk has: an objective lens for irradiating a laser beam to the optical disk; an actuator for moving the objective lens in the radial direction of the optical disk; and a spindle motor for rotating the optical disk. After the laser beam irradiated to the optical disk passed through a PID portion of the optical disk, the actuator moves the objective lens in the radial direction of the optical disk at a timing corresponding to a rotational speed. Between signals to drive the actuator, an output time of a deceleration signal is set to a predetermined ratio of a time during which an acceleration signal is outputted. While the deceleration signal is outputted, a light spot passes through the PID portion.

INCORPORATION BY REFERENCE

The application is a continuation application of U.S. patent applicationSer. No. 11/503,104, filed on Aug. 11, 2006, which claims priority fromJapanese Patent Application JP2005-335125, filed on Nov. 21, 2005, thecontent of both of which are hereby incorporated by reference into thisapplication.

BACKGROUND OF THE INVENTION

The invention relates to an optical disk apparatus having an opticalpickup and, more particularly, to a track jump on an optical disk.

There has been proposed a track jump method whereby when an abnormalityhas occurred in a track jump of an optical disk, a scanning position ofthe track is stored and a track jump command is outputted at the timingwhen the track jump does not overlap at such a position (refer toJP-A-5-205287).

By using such a method, when a rotational speed of the optical disk isequal to a low-times speed (low×speed), the track jump can be executedso as not to overlap a PID portion.

SUMMARY OF THE INVENTION

In the related art of JP-A-5-205287 mentioned above, nothing isconsidered with respect to the case where the rotational speed is set toa high-times speed (high×speed) and it cannot be avoided that the PIDportion enters during the track jump.

When the realization of higher-times speed of a DVD-RAM progresses,since the track jump cannot be executed within one sector (between thePID and the PID) any longer, the track jump has to be executed over twosectors.

This is because although it takes a time of about 200 to 300 μsec forthe track jump, a time which is required until a laser beam passesthrough the next PID after passing through the PID is equal to about 300μsec for a 5-times speed and the laser beam passes through the PIDduring the track jump when a recording speed or a reproducing speedexceeds the 5-times speed.

As shown in FIGS. 2A and 2B, if the light spot passes through the PIDbefore a deceleration end threshold, timing to finish a decelerationvoltage is erroneously set, making a deceleration insufficient, and thelight spot cannot be pulled in to a target track, so that there is afear that the track jump fails and the reproducing operation or therecording operation of the disk fails.

It is, therefore, an object of the invention to solve the foregoingproblems and provide an optical disk apparatus having high reliability.

To accomplish the above object, according to one aspect of theinvention, there is provided an optical disk apparatus for recording andreproducing information to/from an optical disk, comprising: an opticalpickup having a semiconductor laser for emitting a laser beam to beirradiated onto the optical disk, an objective lens, an actuator, and aphotodetector for detecting reflection light from the optical disk; aspindle motor unit for rotating the optical disk; error signal formingmeans for forming a tracking error signal representing a relativeposition in the radial direction between the objective lens and a trackof the optical disk from an output signal of the photodetector; actuatordriving means for driving the actuator; spindle motor driving means fordriving the spindle motor; and system control means for obtaining thetracking error signal from the error signal forming means, outputting atracking drive signal to the actuator driving means, and outputting aspindle drive signal to the spindle motor driving means, wherein whenthe actuator performs a track jump, after the laser beam irradiated tothe optical disk passed through a PID of the optical disk, anacceleration signal is outputted from the system control means so as tomove the objective lens in the radial direction of the optical disk at atiming according to a rotational speed of the optical disk, the signalis switched from an acceleration to a deceleration on the basis of thetracking error signal, and a deceleration time is set to a time of acertain predetermined ratio of the acceleration time, so that even ifthe laser beam transverses the PID during the output of a decelerationsignal and the tracking error signal is disturbed, the track jump can beperformed without being influenced by the disturbed tracking errorsignal.

Just before the laser beam passes through the PID of the optical disk,the system control means adjusts the timing and outputs the accelerationsignal. While the light spot is transversing the PID, the system controlmeans ignores the tracking error signal. After the laser beamtransversed the PID, the system control means switches the signal fromthe acceleration to the deceleration on the basis of the tracking errorsignal and allows the deceleration signal to be outputted only for thedeceleration time corresponding to the certain predetermined ratio ofthe acceleration time. Thus, even if the light spot transverses the PIDagain during the deceleration, the track jump is not influenced by it.

According to the invention, the optical disk apparatus with the highreliability in which the track jump can be stably performed can beprovided.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are explanatory diagrams of the fundamental operation ofa track jump;

FIGS. 2A and 2B are explanatory diagrams of the operation when the trackjump fails;

FIG. 3 shows an optical disk apparatus;

FIGS. 4A and 4B are explanatory diagrams of the track jump operation;

FIGS. 5A and 5B are explanatory diagrams of the track jump operation;

FIGS. 6A and 6B are explanatory diagrams of the track jump operation;and

FIG. 7 is a flowchart.

DESCRIPTION OF THE EMBODIMENTS

An embodiment of the invention will be described hereinbelow withreference to the drawings. Similar component elements in the drawingsare designated by the same reference numerals.

As an optical disk apparatus of the invention, any one of a read onlyapparatus, a recording only apparatus, and a recording and reproducingmay be used so long as it can discriminate an optical disk.

There has been developed an optical disk apparatus corresponding to aDVD-RAM disk in which data is recorded onto an optical disk havinggrooves and lands of a predetermined length disposed spirally orconcentrically for recording data and having a plurality of sectors eachof which is constructed by a header portion consisting of address dataand a data area in which the data is recorded, or the data recorded onthe optical disk is reproduced, and a PID (Physical ID) as address dataof the header portion has been alternately formed for the groove and forthe land.

In the optical disk apparatus, a track jump to move a light spot to anadjacent track is controlled by using a tracking error signal. As shownin FIGS. 1A and 1B, although a waveform of the tracking error signalchanges in accordance with the movement of the light spot between thetracks, in the control of the track jump, it is particularly importantto control an acceleration voltage and a deceleration voltage inaccordance with timing when the light spot passes through a boundarybetween the tracks. This is because the track jump is realized byswitching the acceleration voltage to the deceleration voltage at thetiming when the tracking error signal transverses anacceleration/deceleration switching threshold, finishing the supply ofthe deceleration voltage at the timing when the tracking error signaltransverses a deceleration end threshold, and switching a control modeto a normal feedback control.

However, in a DVD-RAM driving apparatus or the like, when the light spottransverses the PID at the time of the track jump, the tracking errorsignal is caused to change and the switching between the accelerationand the deceleration by a tracking drive signal is not normallyperformed. Therefore, it is necessary to perform the track jump so thatthe light spot do not transverse the PID.

Embodiment 1

FIG. 3 is a block diagram showing a construction of an optical diskapparatus according to the invention.

Reading, erasure, and writing of information of the optical disk 100 areexecuted to/from an optical disk 100 by irradiating a laser beam from anoptical pickup 110. The optical disk 100 is rotated by a spindle motor101 which is driven by a spindle motor driving unit 121 which received asignal from a system control unit 120.

The laser beam emitted from a semiconductor laser 111 is converged ontoan information recording surface of the optical disk 100 by an objectivelens 113 which is moved in the radial direction of the optical disk 100by an actuator 112, reflected, and detected by a photodetector 114. Atracking error signal formed by an error signal forming unit 122 fromthe signal detected by the photodetector 114 is inputted to the systemcontrol unit 120. An actuator driving unit 123 drives the actuator 112by a tracking drive signal which is outputted from the system controlunit on the basis of information of the tracking error signal, therebymoving the objective lens 113 in the radial direction of the opticaldisk 100.

FIGS. 4A and 4B show a motion of the light spot at the time of the trackjump and the tracking error signal and the tracking drive signalaccording to the invention. After the system control unit 120 outputsthe acceleration voltage to the tracking drive signal, while detectingthe tracking error signal, it moves the actuator in the jumpingdirection, measures an acceleration time A which is required until thetracking error signal transverses an acceleration/deceleration switchingthreshold, does not set the deceleration end threshold, but outputs thedeceleration voltage only for a deceleration time B corresponding to acertain predetermined ratio of the acceleration time A. Assuming thatsuch a ratio is denoted as α, the deceleration time B is expressed bythe following equation.

B=α×A

By virtue of this, even if the light spot transverses the PID during thedeceleration, the deceleration can be performed for a predetermined timewithin the acceleration time A without being influenced by thetransversing. Although the deceleration end threshold is not set in theabove explanation, a similar effect is obtained even if the decelerationend threshold is set to a level which is equal to or larger than anamplitude of the tracking error signal.

By setting a waiting process after the passage through the PID, thetiming to start the track jump is adjusted. The time for the waitingprocess is set in such a manner that the light spot does not transversethe PID during the acceleration but the light spot transverses the PIDalmost at the center of the deceleration time in order to cope with avariation. In the DVD-RAM, since the number of PIDs gets larger as aposition approaches an outer rim (periphery) closer, assuming that arotating system of the disk is the constant angular velocity(hereinafter, abbreviated to “CAV”), a time interval between the PIDs inan inner rim portion of the disk differs from that in an outer rimportion. It is preferable to set a waiting time every zone in order tocope with such a problem.

By outputting the acceleration signal and the deceleration signal by amethod similar to that mentioned above, the invention can be alsoapplied to a half-track jump from the land to the groove or from thegroove to the land.

Embodiment 2

FIGS. 5A and 5B show the motion of the light spot at the time of thetrack jump and the tracking error signal and the tracking drive signalaccording to the invention with respect to the case where an appearancefrequency of the PIDs is shorter than that in the case of the embodiment1 and it is difficult to cope with such a situation by the method of theembodiment 1. A construction of an optical disk apparatus of theembodiment 2 is substantially the same as that in the embodiment 1.

In a manner similar to the embodiment 1, it is assumed that thedeceleration time B is equal to a certain predetermined ratio of theacceleration time A. The system control unit 120 sets the time for thewaiting process so that the light spot transverses the PID immediatelyafter the start of the acceleration.

Even if the tracking error signal transverses theacceleration/deceleration switching threshold together with the start ofthe acceleration, the system control unit 120 inserts an error signalignoring process P for ignoring such a situation, thereafter, detectsthe tracking error signal, and detects that the tracking error signaltransverses the acceleration/deceleration switching threshold. A timefor the error signal ignoring process P is set to a time which isrequired until the light spot transverses the PID and until the timingbefore the tracking error signal transverses theacceleration/deceleration switching threshold.

The system control unit 120 inserts an error signal ignoring process Qafter the tracking driving voltage is switched to the deceleration. Evenif the tracking error signal transverses the deceleration end threshold,it is ignored, thereby allowing the deceleration voltage to be outputtedfor the deceleration time B corresponding to only a certainpredetermined ratio of the acceleration time A. A time for the errorsignal ignoring process Q is set to be long enough to sufficiently coverthe deceleration time B.

By combining the embodiments 1 and 2, it is possible to use a methodwhereby in the inner rim portion and the middle portion of the opticaldisk 100 which is rotated at the CAV, the track jump is performed by themethod of the embodiment 1, while in an outer rim portion, the trackjump is performed by the method of the embodiment 2.

Embodiment 3

FIGS. 6A and 6B show the motion of the light spot at the time of thetrack jump and the tracking error signal and the tracking drive signalaccording to the invention with respect to the case where an appearancefrequency of the PIDs is shorter than that in the case of the embodiment1 and it is impossible to cope with such a situation by the method ofthe embodiment 1. A construction of an optical disk apparatus of theembodiment 3 is substantially the same as that in the embodiment 1.

In the embodiment 3, an acceleration voltage X and a decelerationvoltage Y are set to be higher than an acceleration voltage V and adeceleration voltage W in the embodiment 1. Therefore, a moving speed ofthe objective lens 113 is raised and a moving time can be shortened.

By using the method of the embodiment 3, the time which has been set forthe optical disk 100 every zone in the embodiments 1 and 2 can be usedfor different rotational speeds. That is, even if the rotational speedsdiffer, by changing the voltage levels of the acceleration and thedeceleration, it is possible to cope with such a situation by onewaiting time for one zone. Therefore, if the waiting time has beenpreset every zone into a memory or the like of the optical diskapparatus, it is sufficient merely to change the voltage in accordancewith the rotational speed. There is no need to prepare a parameter tableof the waiting times every rotational speed.

Embodiment 4

The embodiment 4 shows a method whereby the time which has been set forthe optical disk 100 every zone in the embodiments 1 and 2 is used forthe different rotational speeds. A construction of an optical diskapparatus of the embodiment 4 is substantially the same as that in theembodiment 1.

In both of the embodiments 1 and 2, the acceleration voltage and thedeceleration voltage are constant irrespective of the zones and thewaiting time is set every zone. When the rotational speeds differ, thetime which is necessary for the light spot to transverse the PID varies.Therefore, it is necessary to set the table of the waiting time everyrotational speed to which the optical disk apparatus corresponds.

To this end, the table of the waiting time is made to be adapted to aplurality of rotational speeds by changing the voltage level like anembodiment 3. The embodiment 4 shows a method whereby when the opticaldisk 100 is inserted into the optical disk apparatus, by adjusting thevoltage level, the table of the waiting time is made to be adapted to aplurality of rotational speeds.

An adjusting method of the voltage level will be explained withreference to a flowchart of FIG. 7.

In step 1, both of the acceleration voltage and the deceleration voltageare set to an initial voltage level V₀. The initial voltage level haspreviously been stored in the optical disk apparatus.

In step 2, the track jump is performed. At this time, although the trackjump may be performed in any zone, since the number of PIDs is smalleras the position approaches the inner rim portion closer, it is desirableto perform the track jump in the inner rim portion.

In step 3, a time Ta required for the acceleration of the track jump ismeasured. Proper times corresponding to the time which is required forthe acceleration suitable for the rotational speed have previously beenstored in the optical disk apparatus. Such times are now assumed to be apermissive time T_(x)−T_(y)(T_(x)<T_(y)).

In step 4, whether or not the measured acceleration time Ta lies withinthe permissive time T_(x)−T_(y) is discriminated.

If T_(a)<T_(x) as a discrimination result of step 4, since the voltagelevel is too large, the voltage level is decreased in step 5 and,thereafter, the processing routine is returned to step 3.

If T_(a)>T_(y) as a discrimination result of step 4, since the voltagelevel is too small, the voltage level is increased in step 6 and,thereafter, the processing routine is returned to step 3.

If T_(x)≦T_(a)≦T_(y) as a discrimination result of step 4, the voltagelevel is determined to be proper and the voltage is set to this level instep 7.

By using the method of the embodiment 4, unlike the embodiment 3, it ispossible to cope with a variation in sensitivity of the actuator. Evenif characteristics of the actuator differ depending on a difference oftemperature situations, the voltage level according to such a situationcan be set.

It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

1. An optical disk apparatus for reproducing information from orrecording information to an optical disk, comprising: an objective lenswhich forms a light spot onto a data recording film of said opticaldisk; an actuator which moves said objective lens in a radial directionof said optical disk, and a photodetector which detects reflection lightfrom said optical disk; an error signal forming portion which forms atracking error signal from a signal which is outputted from saidphotodetector; a controller which outputs a tracking drive signal on thebasis of said tracking error signal; and an actuator driver which drivessaid actuator on the basis of an actuator control signal which isoutputted from said controller, wherein an acceleration signal and adeceleration signal which are outputted from said controller to saidactuator driver in order to move said objective lens in the radialdirection, wherein the length of said acceleration signal output timeand deceleration signal output time varies in accordance with a periodfrom when said acceleration signal is outputted until said trackingerror signal reaches a predetermined value after coming through a localmaximum value or a local minimum value, wherein said deceleration signaloutput time varies in direct relation with said acceleration signaloutput time such that said deceleration signal output time becomesshorter as said acceleration signal output time becomes shorter and saiddeceleration signal output time becomes loner as said accelerationsignal output time becomes longer.